Fcγ Receptor Expression on Sheep Afferent Lymph Dendritic Cells and Rapid Modulation of Cell Surface Phenotype Following Fcγ Receptor Engagement In Vitro and In Vivo

Afferent lymph dendritic cells were analysed for the presence of Fcγ receptors by Western blotting and for modulation of surface markers following Fcγ receptor engagement in vitro and in vivo . The results showed thatunstimulated dendritic cells expressed FcγRII constitutively. When dendritic cells were incubated in vitro with antigen/antibody complexes in antibody excess, a marked reduction in surface staining was observed for MHC class II, CD1, CD44,and VLA-4 after 8 h in culture. These changes did not occur with antigen or antibody alone. DC expression of LFA-1 and LFA-3 were slightly reduced after 8 h in culture with Ova alone, but this was enhanced slightly when the cells werecultured with immune complexes. Even more marked reductions in surface staining for MHC class II, CD1, CD44 and VLA-4 were observed on dendritic cells 4–8 h following secondary antigen challenge in vivo . LFA-1 and LFA-3 expressionwas reduced only slightly. The level of expression of MHC class II, CD1, LFA-1 and LFA-3 was substantially increased over resting values 24 h after FcγR occupancy. The intensity of staining at this time was also significantly elevated for CD44, LFA-1, LFA-3 and VLA-4. These results show that engagement of Fcγ receptors cause a substantial modulation of the dendritic cell surface phenotype after immune complex uptake. The phenomenon may function to maximize subsequent presentation of thechallenge antigen to T cells.